Most archeologists agree that the Americas were originally populated
by
peoples from Asia, who moved during the period of the last Ice Age
when the
level of the oceans fell. Possibly due to increasing population
pressure, Homo
sapiens sapiens in Europe and Asia had been able to move onto the
northern
steppes and tundra by about 20,000 B.C. and by that time were
hunting large
game, wearing clothes, and living in small groups. These people
moved across
the land bridge that formed in the present Bering Strait between
Siberia and
Alaska. During the last period of the Pleistocene, or Ice Age
(Wisconsin
glaciation), the capture of great quantities of water in the ice
lowered the
level of the oceans and made it possible to cross from Siberia to
Alaska on
dry land.

Perhaps one-third of the earth's surface was under ice during the
greatest extent of the expanding glacial sheets. The land bridge
itself was
not covered with ice but was probably a grassy tundra. The mammoths,
mastodons, ancestors of the bison, and other large game probably
followed this
route, and the hunters followed after. A subsequent rise in the
world's
temperature about 10,000 years ago caused the ice to melt and
eventually
raised the level of the oceans so that the land bridge disappeared
and the
land migrations from Asia stopped. The last migrations by the
ancestors of the
Inuit (Eskimos) and Aleuts were probably made in boats or across the
polar
ice.

The Ancient Hunters

These migrations took place over a long period between about 20,000
B.C.
and 8,000 B.C. The earliest definite archeological evidence of
people in the
Americas dates from about 9500 B.C., but many scholars believe that
occupation
is much older than that. Some evidence from South America points to
human
presence by at least 20,000 B.C., but that leaves unexplained the
lack of such
evidence farther north along the track of the supposed migration.
How long it
took for the area of the American continents to be occupied is open
to
question; it may have taken thousands of years, but one scholar has
estimated
that from a group of only 25 original migrants that doubled every
generation,
a population of 10 million would result in 500 years. A population
of 10
million, or about 1 person per square mile, seems reasonable for
these peoples
given what we know about more modern hunting societies, but other
scholars
have estimated the whole world's population before agriculture at
only 10
million.

The earliest migrants may have had a technology that did not include
projectiles (spears) since the only evidence of their tools are
small stones
used for scraping or cutting. Crude spearheads, associated with the
remains of
animals that became extinct about 12,000 years ago, document the
presence of
hunting bands in the Americas. By about 11,000 years ago stone tools
and
simple spear points (with short side channels or flutes allowing
them to be
bound onto shafts) associated with these early hunters were widely
dispersed
over North America. Originally discovered at Clovis, New Mexico,
these
projectile points demonstrate widely shared techniques of
production.

Other tool traditions followed, some of them relatively localized.
In New
Mexico between 11,000 and 9,000 years ago, Folsom points were
beautifully
crafted with a flute that ran the length of the blade. These are
usually found
in conjunction with the bones of the ancestor of the bison. By about
6000 B.C.
a longer, well-crafted point was in use for hunting not only the
ancient
long-horned bison, but also antelope and the modern bison.

As the climate became dryer and warmer, the ice began to melt. The
great
mammal herds diminished and some of the species disappeared. The
ancient
Americans seem to have been particularly successful hunters, and it
has been
argued that the disappearance of animals such as the mammoths, the
ancient
horse, the camel, and the giant anteater was, at least in part, due
to the
hunters' skills. After all, the climate changed in Eurasia as well,
but
nowhere else in the world did the number of mammals that became
extinct equal
that of the Americas, especially North America.

Little is known about the society of these early Ice Age hunters.
Most
likely, they lived in small groups or bands of 20 to 25 people,
following the
game in a seasonal pattern. Sites where the bones of the hunters'
kills are
found indicate that these people probably hunted the mammals in
large groups.
Kinship provided the basis of social organization, and there was
little
specialization or hierarchy in society. Age and gender were the main
determinants of a person's roles and what he or she contributed to
the group.

[See Early Spearheads: Early spearheads indicating the presence of
human
populations in the Americas by 10,000 B.C. were discovered at Folsom
(2nd from
right) and Clovis (center), New Mexico. Folsom points found in 1927
in
conjunction with extinct bison species changed scientific thinking
about the
timing of human occupation in the New World.]

American Diversity

Over the long period of the migrations, different peoples of
different
physical types and languages came out of Asia. Some of the first
migrants came
into the Western Hemisphere prior to the predominance of the
Mongoloid peoples
in Asia. Consequently there were Caucasoid and Australoid genetic
features in
the ancestors of the first Americans, or what are sometimes called
the
Paleo-Indians. The fact that all Indians of South America are of
blood type O
while in Asia type B predominates indicates the diversity of
physical types
involved in the migration and perhaps the early date of the
migration prior to
the creation of the present genetic situation of Asian populations.
The
Eskimos (Inuit), who genetically are most like contemporary Asians,
were
probably the last group to migrate.

While there was considerable physical variation among the American
Indian
populations, the genetic and physical similarity among them is very
strong.
This indicates a large degree of common ancestry and a relative
isolation from
other human populations. The variations among Indians can be
attributed to
adaptations and localized natural selection.

American Indian languages also display considerable diversity. There
were
over 2000 languages spoken in the Americas when Europeans arrived in
the 16th
century. While scholars differ in interpreting linguistic data,
there is
general agreement that there were a number of language groups or
parent
language stocks. People of related languages may have shared
cultural elements
at one time, but peoples of widely differing cultures sometimes
spoke similar
languages. For example, the nomadic Utes and the city-dwelling
Aztecs spoke
related tongues.

Language, however, can be used to trace the movement of peoples. The
Navajo and Apaches of the American Southwest speak Athapascan
languages
related to the speech of the inhabitants of northwestern Canada and
Alaska,
and quite unlike that of their Pueblo neighbors. It is assumed that
they were
later migrants who split off from their linguistic relatives to the
north.

Outside Contacts?

The problem of later contacts with the Americas across the Pacific
or the
Atlantic continues to fascinate archeologists and cause heated
debate.
Definite mysteries and gaps in the history of pre-Columbian cultures
remain
unresolved. Artistic motifs and styles similar to those of Shang
China and
Southeast Asia seem to indicate contact. Early pottery found at
Valdivia on
the coast of Ecuador seems remarkably like Japanese Jomon-period
ceramics.
Plants, such as cotton and bottle gourds, seem of definite Old World
origin
and their presence in the Americas suggests diffusion by human
agents. While
many scholars admit the possibility of sporadic transoceanic
contacts with
Chinese, Phoenicians, Polynesians, and others, the evidence is still
mostly
circumstantial. No identifiable Old World object has ever been
positively
identified in a pre-Columbian archeological site, and if Phoenicians
or
Chinese introduced pottery or writing to the Americas, why they
failed to
introduce the wheel or bronze at the same time remains an unanswered
question.

The biological and archeological records indicate that the peopling
of
the Americas had taken place long before the beginnings of
agriculture in the
Old World and that, with the disappearance of the Bering land
bridge, this
population had lived in comparative isolation from the rest of
humankind.
While some archeologists have argued that the invention of
agriculture and
pottery may have taken place only once and then been diffused all
over the
world, most scholars believe that the peoples of the Americas
developed
agriculture, domestication of animals (except perhaps the dog),
weaving,
ceramics, complex societies, urbanism, numerical systems, and
religious ideas
- in short, their cultures - independently of the Old World. Still,
occasional
contacts were possible and the introduction of ideas and material
things from
elsewhere into American Indian cultures certainly may have taken
place.

The processes of cultural development and the growth of Indian
civilizations were long and complex, and they gave American Indian
societies
and cultures great resilience and an ability to survive even the
shock of
conquest. This independent development and relative isolation also
had some
negative results when American Indian populations came into contact
with the
peoples of Europe, Africa, and Asia. The development of a technology
that did
not include the wheel, the plow, or iron tools and weapons put
American
Indians at a disadvantage. Dogs, turkeys, and the guinea pig were
domesticated, but with the exception of the llama in the Andes, the
lack of
large mammals, cattle, and horses was also a disadvantage in terms
of diet,
transportation, and power. With the exception of a limited area in
the high
Andes, pastoralism, so important in the Old World, was not a way of
life in
the Americas. Most importantly, the relative isolation of American
populations
from the disease environment of the larger Old World populations
left the
inhabitants of the Americas with no immunities to a number of
diseases that
became endemic in Asia, Europe, and Africa. This would prove
disastrous after
permanent contact was established.